#include <bits/stdc++.h>

using namespace std;
const int N = 100;

long long f[N];

int main()
{
    f[1] = 1;
    f[2] = 2;
    for (int i = 3; i < 100; ++i)
    {
        f[i] = f[i - 1] + f[i - 2];
    }
    int n;
    while (cin >> n)
    {
        cout << f[n] << endl;
    }
    return 0;
}